The invention relates to a multi-disc brake, in particular for a commercial road vehicle.
Multi-disc brakes are used both as dry and wet brakes, in particular in slow-moving, heavy agricultural and construction machinery. In commercial road vehicles, such as heavy goods vehicles or buses, such multi-disc brakes have not yet come into use, although they have considerable advantages over presently used disc brakes. In particular, they have very low wear and operate at a lower temperature level.
Standing in the way of their use in the field of road vehicles are the high residual drag moments of this brake construction as well as rattling noises produced by the brake discs mounted floatingly in toothed or stud guides. This floating mounting also in some cases entails very high wear of the guide parts.
Both the residual drag moments and the rattling noises are the result of wobbling movements, especially of the rotating brake discs, which occur during driving operations.
The cause of these wobbling movements lies essentially in the fact that the concerned rotating brake discs represent a gyroscopic system which reacts with compensating movements to forces acting from outside, accelerations and position changes. These compensating movements, also known as precession and nutation, lead to partial abutment of the rotating brake discs against the plates retained non-rotatably, producing undesired and uneven wear both on the brake discs and on the plates. In addition, the sliding guide system of the rotating discs is subjected to considerable wear.
It is therefore the object of the invention to develop a multi-disc brake of the above-mentioned type such that its applicability is improved and that, in particular, it can be utilized in fast-moving road vehicles with an economically justifiable service life.
This object is achieved by a multi-disc brake, in particular for a road vehicle, comprising plates arranged non-rotatably parallel to and spaced apart from one another, between each of which a respective rotatable brake disc is positioned. The radially extending plates and the brake discs are able to be pressed against one another while overcoming a clearance during braking and to separate from one another while forming a clearance upon release of the brake. In the unbraked position, the brake discs are pressed individually and/or as a block by axially acting return springs against an axially fixed stop, which is rotatable with the brake discs.
In accordance with the invention, each of the rotating brake discs is held in a stop-limited position in a non-actuated state of the brake.
The wobbling movements described with reference to the state of the art and the high wear resulting therefrom are therefore effectively prevented, as also are rattling noises.
The wobbling movements mentioned are also prevented at relatively high rotational speeds of the brake discs, so that the novel multi-disc brake can be used non-problematically in fast-moving road vehicles, in particular commercial road vehicles such as heavy goods vehicles or buses. The fundamental advantages of a multi-disc brake can therefore be exploited in this field also.
According to an advantageous development of the invention, there is provided a stop against which the brake disc on the actuation side rests in the unbraked position, in which brake disc at least one pressure element is arranged with defined axial displaceability. The pressure element forms for the neighboring brake disc a stop adapted to the state of wear. The pressure element therefore serves to compensate increased clearance caused by wear.
This neighboring brake disc may also be fitted with pressure elements against which the respective following brake disc rests.
In this case, the pressure elements are retained by frictional engagement and, upon application of the associated brake disc, form a force threshold which is higher than the jolting and wobbling forces acting during driving operation. However, upon actuation of the brake this force threshold is overcome and the clearance is reduced until frictional contact is attained.
For example, in the case of increased clearance caused by wear, the pressure element is displaced by the increasing application force so far into the press-fit seating in the brake disc that a sufficiently high braking effect is achieved.
The pretensioning of the whole disc block consisting of the rotating brake discs and the non-rotating plates is achieved according to the invention by use of one or more return springs which bear against the last brake disc oriented away from the stop with a force in the direction of the stop. The individual brake discs of the block are tensioned by way of their pressure elements and rest jointly with sufficient force against the stop via the first brake disc oriented towards the stop.
The stop is rigidly connected to a wheel hub to which the brake discs are fastened non-rotatably. In this case, the stop may be arranged equally on the application side and on the side oriented away therefrom.
The alternative solution according to the invention provides that in the unbraked position the brake discs are pressed individually by axially acting return springs against stops which are rotatable with the brake discs but are axially fixed.
In this variant the respective stop is oriented towards the actuation side; that is, the respective return spring presses the brake disc towards the actuation side.
Upon actuation of the brake, the brake discs are brought successively into frictional contact with the non-rotating plates. The first brake disc allocated to the actuation side comes first into contact with the first plate. After the spring force of the return spring of the first disc has been overcome, this disc is displaced until it comes into contact with the second plate. In the same way, the remaining brake discs are brought successively into contact with the associated plates.
This embodiment is especially advantageous in brakes which have only two brake discs, such a multi-disc brake being distinguished by its simple construction, which makes possible very cost-effective manufacture.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.